Hi
This was discussed some months ago and a setting was introduced "order status to delete gift coupons".
However the problem is that when a user introduces a gift coupon this one gets marked as "used" and the customer has one try to make use of it.
If the order with the coupon applied gets cancelled or remains pending he wont be able to use it again.
vm 3.0.6.4 joomla 3.4.1